Re: [PATCH] nbd: fix crash when the blksize is zero

[Xiubo Li]

On 2019/5/30 2:55, Mike Christie wrote:

On 05/27/2019 12:44 AM, xiu...@redhat.com wrote:

From: Xiubo Li <xiu...@redhat.com>

This will allow the blksize to be set zero and then use 1024 as
default.

Signed-off-by: Xiubo Li <xiu...@redhat.com>
---
  drivers/block/nbd.c | 21 ++++++++++++++++++---
  1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 053958a..4c1de1c 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -135,6 +135,8 @@ struct nbd_cmd {

#define NBD_MAGIC 0x68797548 +#define NBD_DEF_BLKSIZE 1024

+
  static unsigned int nbds_max = 16;
  static int max_part = 16;
  static struct workqueue_struct *recv_workqueue;
@@ -1237,6 +1239,14 @@ static void nbd_clear_sock_ioctl(struct nbd_device *nbd,
                nbd_config_put(nbd);
  }

+static bool nbd_is_valid_blksize(unsigned long blksize)

+{
+       if (!blksize || !is_power_of_2(blksize) || blksize < 512 ||
+               blksize > PAGE_SIZE)
+               return false;
+       return true;
+}
+
  /* Must be called with config_lock held */
  static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
                       unsigned int cmd, unsigned long arg)
@@ -1252,8 +1262,9 @@ static int __nbd_ioctl(struct block_device *bdev, struct 
nbd_device *nbd,
        case NBD_SET_SOCK:
                return nbd_add_socket(nbd, arg, false);
        case NBD_SET_BLKSIZE:
-               if (!arg || !is_power_of_2(arg) || arg < 512 ||
-                   arg > PAGE_SIZE)
+               if (!arg)
+                       arg = NBD_DEF_BLKSIZE;
+               if (!nbd_is_valid_blksize(arg))
                        return -EINVAL;
                nbd_size_set(nbd, arg,
                             div_s64(config->bytesize, arg));
@@ -1333,7 +1344,7 @@ static struct nbd_config *nbd_alloc_config(void)
        atomic_set(&config->recv_threads, 0);
        init_waitqueue_head(&config->recv_wq);
        init_waitqueue_head(&config->conn_wait);
-       config->blksize = 1024;
+       config->blksize = NBD_DEF_BLKSIZE;
        atomic_set(&config->live_connections, 0);
        try_module_get(THIS_MODULE);
        return config;
@@ -1769,6 +1780,10 @@ static int nbd_genl_connect(struct sk_buff *skb, struct 
genl_info *info)
        if (info->attrs[NBD_ATTR_BLOCK_SIZE_BYTES]) {
                u64 bsize =
                        nla_get_u64(info->attrs[NBD_ATTR_BLOCK_SIZE_BYTES]);
+               if (!bsize)
+                       bsize = NBD_DEF_BLKSIZE;
+               if (!nbd_is_valid_blksize(bsize))
+                       return -EINVAL;

You can't only return here. You need to also drop the mutex, do
nbd_put, and drop config_refs reference.

Maybe you want to move this check to the beginning of the function with
the NBD_ATTR_SIZE_BYTES sanity check since the error handling is easier
there.

Yeah, right.

I saw your resend patch of this and that looks good to me.

Thanks
BRs
Xiubo

                nbd_size_set(nbd, bsize, div64_u64(config->bytesize, bsize));
        }
        if (info->attrs[NBD_ATTR_TIMEOUT]) {